The correct answer is A. Silicon Dioxide.
Quartz crystals are naturally occurring minerals that are composed of silicon and oxygen atoms. They are very hard and brittle, and they have a piezoelectric property, which means that they can generate an electric charge when they are deformed. This property makes them useful in a variety of applications, including quartz clocks, watches, and oscillators.
Germanium oxide is a chemical compound with the formula GeO2. It is a white, odorless, tasteless solid that is insoluble in water. Germanium oxide is used in a variety of applications, including semiconductors, optical fibers, and ceramics.
A mixture of germanium oxide and silicon dioxide is not a common material. It is possible to create such a mixture, but it would not have the same properties as quartz crystals.
Sodium silicate is a chemical compound with the formula Na2SiO3. It is a white, water-soluble solid that is used in a variety of applications, including glassmaking, detergents, and adhesives. Sodium silicate is not a piezoelectric material, and it would not be suitable for use in quartz clocks.